Engine bogs down has no power when warmed up.
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Freshman User
Joined: Sep 2009
Posts: 43
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From: Wisconsin
Engine bogs down has no power when warmed up.
I need help! I have a 78 f250 with a 351m. Truck is all original and has been stored for the last 3 years. I got it out this spring and had an issue where it would seem to cut out under a load. I thought it was a carb issue and needed a rebuild. I rebuilt the carb and the issue did not change. I tried to be systematic with my diagnosis and replace one thing at a time. As of now, I have replaced the plugs, wires, cap rotor, coil, pick up coil, vacuum advance, pvs and fuel pump. Now the issue I'm having is the truck starts and idles fine and you can Rev the engine, but once it seems to warm up, I can't Rev the engine, it will bog down at 2000 rpms.
I've checked and rechecked timimg, firing order. I am at a loss I can't seem to think of anything else, and I'm afraid I'm at the limit of my expertise. Any advice would be great.
I've checked and rechecked timimg, firing order. I am at a loss I can't seem to think of anything else, and I'm afraid I'm at the limit of my expertise. Any advice would be great.
Senior User
Joined: Mar 2017
Posts: 395
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From: Everton MO
my 300 did the same thing i rebuilt the carb twice to make sure that wasnt the issue, my vacume advance was bad and was hooked to the wrong place on the carb. i could barely get it over the 2 inch lip of my shop door to put it away. it would die and the timing would be off and just a general loss of power. make sure the vac adv is connected to the spark port.
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Freshman User
Joined: Sep 2009
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From: Wisconsin
78Fords, I was convinced it was a timing issue as well. My vacuum advance gets its vacuum from the PVS that is screwed into the thermostat neck. I replaced the PVS just to rule it out, and the vacuum lines are all back in their original spots. Thanks for the advice.
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Freshman User
Joined: Sep 2009
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From: Wisconsin
72rtchallenger, My truck has dual exhaust with glass packs, its had this same set up for years. I got this truck from a family member in 2006 with 29,000 original miles. It ran this same exhaust then as now. Thanks for replying though. sometimes a new thought process is what is needed. I have talked with a local Ford guru, and he suggested that the it sounded like it was starved for fuel and the new fuel pump doesn't necessarily mean it was good. So I did order a new pump tonight. I will replace it again and see if I have better results. In the meantime, keep the suggestions coming, thanks everyone.
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Tuned
Joined: Feb 2014
Posts: 335
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From: USA
What condition is the battery in?
But it really sounds like a carb/fuel issue to me. Have you checked for vapor lock? If you take your gas cap off does it make a whooshing sound?
The old venting on my tank got clogged and couldn't vent properly causing fuel starvation. It would start and idle just fine, but bogged and stalled when I tried to drive it around.
But it really sounds like a carb/fuel issue to me. Have you checked for vapor lock? If you take your gas cap off does it make a whooshing sound?
The old venting on my tank got clogged and couldn't vent properly causing fuel starvation. It would start and idle just fine, but bogged and stalled when I tried to drive it around.
Fleet Mechanic
Joined: Sep 2014
Posts: 1,626
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From: NE Texas
Sounds like you are just throwing parts at the problem without a clear diagnosis. FWIW, you might also check for vacuum leaks - the choke could be more or less compensating when the engine is cold, but when the choke opens you could be running massively lean and consequently powerless. Might also make note of where the vacuum lines go, plug all of them, and see if it runs better - then start reconnecting them one at a time until your condition recurs. Probably a good idea to get hold of a vacuum line drawing and make sure they are all hooked up right (normally the distributor advance is hooked directly to a port at the base of the carburetor or to manifold vacuum, so I kind of wonder at it going to a thermal vacuum switch. Could be right for the engine, though.)
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